The conformational fluctuations of proteins and nucleic acids are being investigated using nuclear magnetic resonance relaxation techniques. Although the static picture of many biopolymers has been fairly well characterized by X-ray crystallography and nuclear magnetic resonance, very little is known of the dynamics in biopolymers. However, the flexible nature of nucleic acids may be important for their interaction with proteins, drugs, or modifying agents. Protein flexibility may be important in catalysis, allosteric control, and energy transfer. Consequently, our studies of nucleic acids using 31P, 13C, and 19F nuclear magnetic resonance examine not only conformational fluctuations in the nucleic acids themselves but the influence of drugs and of binding in protein complexes such as ribosomes and messenger ribonucleoprotein. Studies of protein conformational flexibility entails examination of the influence of inhibitors and protein unfolding agents as well as the native protein itself.